Factory acceptance testing (FAT): scope, checklist and witnessing
A factory acceptance test (FAT) is the structured demonstration, at the manufacturer's works and before shipment, that equipment meets the requirements of the purchase order, specification and design documents. It is the last point at which a defect is the vendor's problem rather than yours.
FAT proves the equipment works as specified in a controlled environment, with the people who built it on hand and spare parts, tooling and test rigs within reach. Everything found after shipment costs multiples of what it costs in the test bay.
A FAT is only as good as its procedure. The test procedure, acceptance criteria and witness points should be reviewed and approved before the equipment is ready — not written the week the vendor wants a release note.
- 01Approve the FAT procedure and acceptance criteria before the test date, not on the day.
- 02FAT proves the equipment; SAT proves it in its real installed environment with real utilities and interfaces.
- 03Every deviation goes on a categorised punch list — A-items block shipment, full stop.
- 04A signed FAT report without test records, calibration certificates and as-run data is not evidence.
What a factory acceptance test is
A FAT is a formal, documented test carried out at the vendor's facility to verify that manufactured equipment — a skid, panel, pump package, pressure vessel, control system, machine or module — conforms to its specification before it is released for shipment. It is executed against an approved procedure, witnessed by the purchaser or an appointed third party, and closed out with a signed report and a punch list.
The commercial logic is simple. In the vendor's works, a fault can be diagnosed by the engineers who designed the equipment, with the test rig connected and spares on the shelf. On site, the same fault means a crane, a shutdown window, mobilisation costs and a schedule hit. Purchase orders normally tie a payment milestone to FAT acceptance for exactly this reason.
FAT vs SAT
FAT and SAT test the same equipment against different questions. Both are usually required; neither replaces the other.
| Factory acceptance test (FAT) | Site acceptance test (SAT) | |
|---|---|---|
| Question answered | Does the equipment meet the specification as built? | Does it work correctly where it is installed, on real utilities and interfaces? |
| Location | Vendor's works or test facility. | Final installed location on the client's site. |
| Environment | Simulated inputs, test rigs, temporary utilities, signal simulators. | Real power, real process media, real network, real ambient conditions. |
| Typical scope | Visual and dimensional, documentation, functional and control logic, performance/no-load runs, safety interlocks, pressure and leak tests. | Installation verification, loop checks against field devices, integrated interface tests, performance under real load, operator training. |
| Who attends | Purchaser or third-party inspector, vendor engineers, sometimes end user. | Commissioning team, contractor, vendor field service, end user operations. |
| Commercial effect | Releases equipment for shipment; often a payment milestone. | Triggers handover, takeover certificate and start of warranty. |
| Cost of a defect | Lowest — fixed in the shop with tooling and spares to hand. | High — crane time, access, shutdown windows, mobilisation. |
What a FAT should cover
Scope varies by equipment type, but a defensible FAT addresses six areas.
Documentation review
Approved-for-construction drawings, bill of materials, material certificates (EN 10204 3.1/3.2 where specified), welding records, NDT reports, calibration certificates for test instruments.
Visual and dimensional
Build against the GA and P&ID, nozzle orientations and elevations, tag numbering, nameplates, painting and coating DFT, cleanliness and preservation.
Construction and materials
Correct materials installed, PMI where specified, torque records, cable schedules, earthing, ingress protection and hazardous-area certification.
Functional and logic
Point-to-point and loop checks, I/O verification, control narrative and sequence testing, alarms, HMI and graphics, communications with simulated field signals.
Performance
No-load and load runs, flow, head, pressure, vibration, noise, temperature rise, thermal imaging, and any contractual performance curve or guarantee point.
Safety and integrity
Hydrostatic or pneumatic pressure and leak tests, relief settings, emergency stops, interlocks and trips, SIL loop proof testing, and lifting-point verification.
FAT hold-point checklist
Use this as the backbone of the FAT section of your ITP. Each line is a point where the test either proceeds or stops.
| Stage | Hold or witness point | Evidence to leave behind |
|---|---|---|
| Pre-FAT, 4–6 weeks out | FAT procedure, acceptance criteria and test schedule reviewed and approved. | Approved procedure revision, comment-resolution sheet. |
| Pre-FAT, 2 weeks out | Vendor readiness confirmed: build complete, pre-FAT dry run done, open NCRs listed. | Readiness declaration, pre-FAT punch list, open-NCR register. |
| Pre-FAT, on arrival | Test instruments in calibration and traceable; test rig configuration verified. | Calibration certificates with valid dates and serial numbers. |
| Stage 1 | Documentation pack verified against the purchase order and specification. | Signed document index, exception list. |
| Stage 2 | Visual and dimensional inspection against approved drawings. | Dimensional record sheet, photographs, coating DFT readings. |
| Stage 3 | Pressure, leak and integrity tests performed and held for the specified duration. | Pressure test chart or log, gauge IDs, test medium and temperature. |
| Stage 4 | Point-to-point, loop checks and I/O verification. | Signed loop check sheets, I/O list with as-tested column. |
| Stage 5 | Functional and control logic tests against the control narrative. | As-run test sheets showing set point, expected and actual result. |
| Stage 6 | Safety functions: E-stops, interlocks, trips, relief devices, alarms. | Trip test record with as-found and as-left settings. |
| Stage 7 | Performance run at contractual duty points, including sustained-run duration. | Performance data set, vibration and noise readings, thermal survey. |
| Stage 8 | Punch list agreed and categorised; disposition of each item recorded. | Signed punch list with categories, owners and dates. |
| Close-out | FAT report signed; release-for-shipment decision made. | FAT report, preservation and packing plan, shipping release note. |
Punch lists and what blocks shipment
No FAT of any size finishes with a clean sheet. What matters is that every deviation is written down, categorised against agreed rules, and given an owner and a date — before anyone signs anything.
| Category | Definition | Effect on shipment |
|---|---|---|
| A | Non-conformance affecting safety, function, performance or code compliance. | Blocks shipment. Must be corrected and re-tested at the works. |
| B | Deviation not affecting function, correctable on site without significant work. | Shipment may proceed with a written agreement, owner and date. |
| C | Cosmetic or documentation items. | Shipment proceeds; closed before handover or final payment. |
Category A items should also raise a non-conformance report so the item is formally controlled and dispositioned, and so repeat failures from the same vendor show up in trend data rather than in three separate punch lists nobody compares.
How non-conformances get controlled
Our NCR pillar covers what goes on the report, the five disposition options and where NCR ends and CAPA begins.
How to witness a FAT properly
Attending a FAT and witnessing one are different activities. These are the habits that separate them.
- Step 01Weeks before the test, not on arrival
Comment on the procedure early
Read the FAT procedure against the specification and the control narrative, and check that acceptance criteria are numeric and testable. "Operates satisfactorily" is not an acceptance criterion.
- Step 02Travel is the second-largest FAT cost after delay
Verify readiness before you travel
Ask for the pre-FAT dry-run results, the open punch list and the calibration certificates. Most wasted FAT trips are visible in these three documents a week beforehand.
- Step 03Record instrument IDs on the test sheets
Check calibration first, on site
Confirm each test instrument's certificate, serial number and validity date before any reading is taken. An uncalibrated gauge invalidates every number recorded through it.
- Step 04As-run values, not expected values
Watch the test, not the paperwork
Insist that results are recorded as they are observed. Test sheets pre-filled before the run, or completed from memory afterwards, are not objective evidence.
- Step 05Agree these cases in the procedure so they cannot be dropped for time
Test the failure cases
Anyone can demonstrate the happy path. Ask for trips, interlocks, loss of signal, loss of power and out-of-range inputs — that is where design assumptions surface.
- Step 06Signature after agreement, never before
Categorise the punch list before signing
Walk the list item by item with the vendor, agree the category, owner and date for each, and be explicit about which items block shipment.
- Step 07Also confirm preservation and packing before shipment
Take the evidence with you
Leave with as-run test sheets, charts, calibration certificates, the signed punch list and photographs. Evidence promised "with the final dossier" has a way of arriving thinner than expected.
Why FATs let defective equipment ship
Procedure approved on the day
Acceptance criteria get written to match what the equipment can already do, so the test cannot fail.
Schedule pressure at the signature
Category A items get reclassified as B on Friday afternoon because the ship date is Monday.
Simulated everything
Every input simulated and no load applied proves the wiring, not the machine.
No calibration check
Readings taken through instruments whose certificates nobody looked at.
Punch list without owners
Items listed with no name and no date are closed by attrition, not by action.
Untested failure paths
Trips and interlocks skipped for time — then discovered during commissioning, on live plant.
Independent witnessing changes the outcome
The party running the FAT is the party that wants the shipment released and the milestone paid. That is not dishonesty, it is incentive. An independent witness working to your specification and your ITP has no reason to accept a reclassified punch item or an untested trip, and the vendor knows it before the test starts.
Need a FAT witnessed at your vendor's works?
We review FAT procedures, attend as your appointed witness worldwide, categorise punch lists and hold the release decision to the specification.
Building the ITP that leads into the FAT?
Our ITP guide covers hold and witness points, acceptance criteria and the evidence each stage must leave behind.
Questions we get on this topic
What is a factory acceptance test (FAT)?
A factory acceptance test is a formal, documented test carried out at the manufacturer's works before shipment to verify that equipment meets the requirements of the purchase order, specification and approved design. It is run against an approved procedure, witnessed by the purchaser or an appointed third-party inspector, and closed out with a signed report and a categorised punch list.
What is the difference between FAT and SAT?
A FAT is performed at the vendor's works using test rigs and simulated inputs to prove the equipment as built meets its specification before shipment. A site acceptance test is performed after installation using real utilities, real process media and real interfaces to prove the equipment works correctly in its installed environment. FAT typically releases the equipment for shipment; SAT typically supports handover and the start of warranty.
What is included in a FAT?
A typical FAT covers documentation review, visual and dimensional inspection against approved drawings, verification of materials and construction, pressure and leak testing where applicable, point-to-point and loop checks, functional and control logic testing against the control narrative, safety interlock and trip testing, and a performance run at the contractual duty points.
Who attends a factory acceptance test?
The vendor's engineering and test personnel run the test. The purchaser attends, usually represented by a project or quality engineer and often an appointed third-party inspector. End-user operations or commissioning staff frequently attend as well, and for regulated or safety-critical equipment a notified body or certifying authority may also witness.
How long does a FAT take?
It depends entirely on scope. A single instrument or small panel may be a few hours; a control system or process skid is typically two to five days; a large integrated package or string test can run one to three weeks. Build contingency into the schedule for retesting after Category A punch items, and agree the retest rules in the procedure beforehand.
What is a FAT punch list?
A punch list is the agreed record of every deviation found during the FAT, each with a category, an owner and a due date. Category A items affect safety, function, performance or code compliance and must be corrected and retested before shipment; Category B items are correctable on site; Category C items are cosmetic or documentation. The list is agreed and signed before the FAT report is closed.
Can equipment ship if the FAT fails?
Not with open Category A items. Deviations affecting safety, function, performance or code compliance must be corrected and retested at the works before release. Category B and C items can travel with a written agreement recording the owner, the corrective action and the closure date, and they should be tracked through to site acceptance and handover.
Is a FAT required by ISO 9001?
ISO 9001 does not name factory acceptance testing, but clause 8.6 requires verification that product and service requirements have been met before release, with documented evidence of conformity and traceability to the releasing authority. Where a purchase order or specification calls for a FAT, that test is the release verification and its report is the evidence.
Witness your next FAT with independent eyes
Procedure review, on-site witnessing at vendor works worldwide, categorised punch lists and a release decision held to your specification.